The invention relates to actuators made of microstructured substrates, with movable parts (such as bending bars or diaphragms) being driven by outside forces relative to a stationary part.
Micromechanical actuators have been employed, for example, as the ejecting elements of ink jet printers, light valves, light relays and the like, wherein the generation of driving forces is achieved electrostatically. This method can be implemented relatively easily and also offers the possibility of requiring only very low powers. On the other hand, it has the disadvantage that, because of the low driving power, the generated forces, particularly control and adjusting forces, are not very large. This is particularly disadvantageous when, for example, a fluid is to be set into motion or is to be stopped. The switching frequency of mechanical, electric or fluidically driven actuators is low.
It is an object of the present invention to provide a micromechanical actuator which, on the one hand, can be driven with a high switching frequency and, on the other hand, generates or emits reproducible finely apportioned actuating forces.
This object is achieved in a micromechanical actuator according to the invention having a stationary part and a movable part, such as a diaphragm, bending bar or rocker. The movable part can be switched to different positions by means of electromagnetic forces, and held in position by electrostatic forces.
The magnetic control of micromechanical actuators provided according to the invention offers multiple advantages in comparison to known processes. When permanent magnets are used, relatively large forces can be generated which, in contrast to electrostatic forces, are largely independent of the control distance of the movable part of the actuator. In addition, the forces can be generated in both directions and can be operated in the on/off switching mode as well as for switching from one position into another position. The actuators according to the invention may be operated with reasonably low electric voltages while nevertheless particularly high adjusting forces are generated magnetically. The actuator according to the invention may be manufactured relatively easily by means of known micromechanical methods, such as etching techniques or other types of microstructuring, as well as by means of manufacturing techniques for integrated circuits (IC's). An important advantage is the integrated construction of the actuator according to the invention, which includes the control and can be implemented in an extremely small space. This feature of the invention is particularly significant with respect to the combination of an electrostatic and magnetic generating of actuating forces, in the preferred embodiment disclosed hereinafter the latter being capable of being utilized for the deflection, bending-out or similar switchover from an inoperative position into an operative position, whereas the electrostatic force which can be applied almost without any power, is used for holding a movable part in the inoperative position.
The principal applications of the invention of microvalves for pneumatic and hydraulic uses for which the suggested actuator is very advantageous here as the result of its small dimensions and small mass. It is particularly easy to use not only for controlling a gas flow, but also for carrying out other actuating and switching functions. A use, for example, as a pneumatic analog/digital converter is advantageous because a binary switching condition on/off or open/shut can easily be reached. When several actuators are arranged in rows and columns (arrays) over a surface, a geometric assignment can easily by implemented, i.e., a surface-type detector or sensor application or an ultrasonic application or a sonar application and other vibrating applications. Light relays, light valves, diffraction grids, mechanical grids, filters, such as microfilters, opto-electronic, fluidic, mechano-electric line and array arrangements and applications are made possible by the invention because of its simple and effective construction in cases in which actuating and control functions must be carried out in a very small space also at a high frequency, including such actuating and control drives as are used in miniature pumps (diaphragm pumps) and miniature actuating motors (linear pushers). The actuator according to the invention m ay be used for the step-by-step as well as for the continuous actuating-force transmission, and may be used not only in the binary operation but also in a multistage manner continuously or discontinouously and for controlling a total flow or a partial flow of a electric current or of sound waves or light waves. It is suitable for working with or without back pressure, as well as with a vacuum.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.